Automatic check damper



Dec. 7, 1937. W` KEMP AUTOMATIC CHECK DAMPER Filed Aug. 27, 1934 2 Y v Inventor W .Kemp

Bygf

Atty

UNITED STATES Patented Dec. 7, 1937 .f

PATENT OFFICE 1 Claim.

My invention relates to an automatic check damper and particularly to a damper adapted for use in the wind box of a forced draft stoker. Such stokers are commonly yequipped with some type of automatic pressure switch to stop the fan, or the fan and Stoker, at high steam pressure and to start the fan, or the fan and stoker, at low steam pressure. It is in connection with such stokers, and especially with those carrying a high wind box pressure, i. e. above two and one-half inches, that my novel form of damper is adapted to be used.

It is the object of my invention to provide the wind box of a forced draft stoker with a damper mechanism which will permit the passage of a sufficient volume of air to accommodate the natural furnace draft but which will, when the forced draft is applied, automatically check such forced draft and then slowly open so as to secure a gradual increase in the pressure. This prevents blowing holes in the fire and the blowing of smoke and re out of the front of the furnace when the fan is started.

In the accompanying drawing, which illustrates one form of damper made in accordance with my invention, Figure 1 is a side view, partly in section and partly in elevation, of a portion of a forced draft stoker wind box to which the damper is applied; Figure 2 is a cross-section on a reduced scale, taken on the line 2-2 of Figure 1; and Figure 3 is a side elevation, also on a reduced scale, showing the parts in a different position.

The numeral 5 indicates the wind box of a forced draft stoker. This wind box, as is usual, is of rectangular cross-section. Extending across the top of the box is a reinforcing plate 6 having down-turned ends 1 forming bearings for a rock shaft 8. The reinforcing plate is secured in position by any suitable means, such as rivets 9 passing through the ends 'I and the side walls of the wind box. Carried by the rock shaft is the main damper I0. This damper extends from substantially the top to the bottom of the box when in its lowered position and is so dimensioned that when its lower edge engages the bottom wall of the box, as shown in Figure 1, it will be inclined at a substantial angle to the perpendicular. The width of the damper is slightly less than that of the box in order to provide openings I I between the side edges of the damper and the side walls of the box. Formed in the damper is a large opening I2. Hinged to the main damper adjacent the upper edge of the opening I2 is a secondary or flap damper I3. The damper I3, when hanging in a vertical position, uncovers the opening i2 but when moved against the main damper, as shown in Figure 3, closes it. The width of the flap damper is somewhat less than that of the main damper and it does not extend to the bottom wall of the box. This provides space around 5 the side and bottom of the ap damper for the passage of natural draft.

The rock shaft 8 is extended at one side of the box and has rigidly secured to it an arm I4. The arm is pivoted at I5 to the upper end of the l0 plunger rod I6 of a dash pot I'I. The lower end of the dash pot is pivoted at I8 to a bracket I9 secured to the side wall of the box. This permits the necessary swinging motion of the dash pot as the arm I4 moves from the position shown l5 in Figure 1 to that shown in Figure 3, or vice versa.

The operation of my damper is as follows: When natural draft is supplied through the wind box, the parts assume .the position shown in Fig- 20 ure 1, the air passing around the sides and bottom of the flap damper and through the opening I2 in the main damper. When forced draft is supplied the increased air pressure will swing the flap damper against the main damper, closing the 25 opening I2. This checks the forced draft as air can noW only pass through the relatively small openings II at the ends of the damper. The area of these openings should be such that the volume of air allowed to pass under the increased pres- 30 sure will be approximately equal to that passing under natural draft. The forced draft pressure now raises the main damper from the position shown in Figure 1 toward and, if the pressure is suiciently high, to the position shown in Fig- 35 ure 3. The action of the dash pot, however, retards the movement to any desired degree so that the change from natural draft volume to full forced draft volume, is gradual and may be caused to consume any predetermined time by 40 the use of a dash pot havingv the desired retarding effect. When the forced draft is cut off, the parts return to the position shown in Figure 1 by gravity. As it is desirable to have this return movement rapid, the dash pot is preferably of the 45 well known type which acts as a retarding means when the plunger is moving in one direction but permits relatively free movement when the plunger is moving in the other direction.

Having fully described my invention, what I 50 claim as new and desire to secure by Letters Patent of the United States is:

In a device of the class described, the combination with a substantially horizontal wind box, of a rock shaft located adjacent the upper wall of the box, a main damper carried by said shaft and extending in an inclined plane toward the lower wall of the box, said main damper being provided with an air opening, an auxiliary damper pivoted to the main damper adjacent the upper edge of said opening to normally depend in position to uncover said opening but to close said opening when moved into parallelism with the main damper by forced draft, and a, .dash pot connected with the main damper to retard the movement; thereof.

WILLIAM KEMP. 

